1 /* 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by the University of 16 * California, Berkeley and its contributors. 17 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 * 33 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 34 * $FreeBSD: src/sys/netinet/tcp_input.c,v 1.107.2.38 2003/05/21 04:46:41 cjc Exp $ 35 * $DragonFly: src/sys/netinet/tcp_input.c,v 1.2 2003/06/17 04:28:51 dillon Exp $ 36 */ 37 38 #include "opt_ipfw.h" /* for ipfw_fwd */ 39 #include "opt_inet6.h" 40 #include "opt_ipsec.h" 41 #include "opt_tcpdebug.h" 42 #include "opt_tcp_input.h" 43 44 #include <sys/param.h> 45 #include <sys/systm.h> 46 #include <sys/kernel.h> 47 #include <sys/sysctl.h> 48 #include <sys/malloc.h> 49 #include <sys/mbuf.h> 50 #include <sys/proc.h> /* for proc0 declaration */ 51 #include <sys/protosw.h> 52 #include <sys/socket.h> 53 #include <sys/socketvar.h> 54 #include <sys/syslog.h> 55 56 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 57 58 #include <net/if.h> 59 #include <net/route.h> 60 61 #include <netinet/in.h> 62 #include <netinet/in_systm.h> 63 #include <netinet/ip.h> 64 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 65 #include <netinet/in_var.h> 66 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 67 #include <netinet/in_pcb.h> 68 #include <netinet/ip_var.h> 69 #include <netinet/ip6.h> 70 #include <netinet/icmp6.h> 71 #include <netinet6/nd6.h> 72 #include <netinet6/ip6_var.h> 73 #include <netinet6/in6_pcb.h> 74 #include <netinet/tcp.h> 75 #include <netinet/tcp_fsm.h> 76 #include <netinet/tcp_seq.h> 77 #include <netinet/tcp_timer.h> 78 #include <netinet/tcp_var.h> 79 #include <netinet6/tcp6_var.h> 80 #include <netinet/tcpip.h> 81 #ifdef TCPDEBUG 82 #include <netinet/tcp_debug.h> 83 84 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */ 85 struct tcphdr tcp_savetcp; 86 #endif /* TCPDEBUG */ 87 88 #ifdef FAST_IPSEC 89 #include <netipsec/ipsec.h> 90 #include <netipsec/ipsec6.h> 91 #endif 92 93 #ifdef IPSEC 94 #include <netinet6/ipsec.h> 95 #include <netinet6/ipsec6.h> 96 #include <netkey/key.h> 97 #endif /*IPSEC*/ 98 99 #include <machine/in_cksum.h> 100 101 MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry"); 102 103 static const int tcprexmtthresh = 3; 104 tcp_cc tcp_ccgen; 105 106 struct tcpstat tcpstat; 107 SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW, 108 &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 109 110 static int log_in_vain = 0; 111 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 112 &log_in_vain, 0, "Log all incoming TCP connections"); 113 114 static int blackhole = 0; 115 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 116 &blackhole, 0, "Do not send RST when dropping refused connections"); 117 118 int tcp_delack_enabled = 1; 119 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 120 &tcp_delack_enabled, 0, 121 "Delay ACK to try and piggyback it onto a data packet"); 122 123 #ifdef TCP_DROP_SYNFIN 124 static int drop_synfin = 0; 125 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 126 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 127 #endif 128 129 struct inpcbhead tcb; 130 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 131 struct inpcbinfo tcbinfo; 132 133 static void tcp_dooptions(struct tcpopt *, u_char *, int, int); 134 static void tcp_pulloutofband(struct socket *, 135 struct tcphdr *, struct mbuf *, int); 136 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, 137 struct mbuf *); 138 static void tcp_xmit_timer(struct tcpcb *, int); 139 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 140 141 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 142 #ifdef INET6 143 #define ND6_HINT(tp) \ 144 do { \ 145 if ((tp) && (tp)->t_inpcb && \ 146 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0 && \ 147 (tp)->t_inpcb->in6p_route.ro_rt) \ 148 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \ 149 } while (0) 150 #else 151 #define ND6_HINT(tp) 152 #endif 153 154 /* 155 * Indicate whether this ack should be delayed. We can delay the ack if 156 * - delayed acks are enabled and 157 * - there is no delayed ack timer in progress and 158 * - our last ack wasn't a 0-sized window. We never want to delay 159 * the ack that opens up a 0-sized window. 160 */ 161 #define DELAY_ACK(tp) \ 162 (tcp_delack_enabled && !callout_pending(tp->tt_delack) && \ 163 (tp->t_flags & TF_RXWIN0SENT) == 0) 164 165 static int 166 tcp_reass(tp, th, tlenp, m) 167 register struct tcpcb *tp; 168 register struct tcphdr *th; 169 int *tlenp; 170 struct mbuf *m; 171 { 172 struct tseg_qent *q; 173 struct tseg_qent *p = NULL; 174 struct tseg_qent *nq; 175 struct tseg_qent *te; 176 struct socket *so = tp->t_inpcb->inp_socket; 177 int flags; 178 179 /* 180 * Call with th==0 after become established to 181 * force pre-ESTABLISHED data up to user socket. 182 */ 183 if (th == 0) 184 goto present; 185 186 /* Allocate a new queue entry. If we can't, just drop the pkt. XXX */ 187 MALLOC(te, struct tseg_qent *, sizeof(struct tseg_qent), M_TSEGQ, 188 M_NOWAIT); 189 if (te == NULL) { 190 tcpstat.tcps_rcvmemdrop++; 191 m_freem(m); 192 return (0); 193 } 194 195 /* 196 * Find a segment which begins after this one does. 197 */ 198 LIST_FOREACH(q, &tp->t_segq, tqe_q) { 199 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) 200 break; 201 p = q; 202 } 203 204 /* 205 * If there is a preceding segment, it may provide some of 206 * our data already. If so, drop the data from the incoming 207 * segment. If it provides all of our data, drop us. 208 */ 209 if (p != NULL) { 210 register int i; 211 /* conversion to int (in i) handles seq wraparound */ 212 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; 213 if (i > 0) { 214 if (i >= *tlenp) { 215 tcpstat.tcps_rcvduppack++; 216 tcpstat.tcps_rcvdupbyte += *tlenp; 217 m_freem(m); 218 free(te, M_TSEGQ); 219 /* 220 * Try to present any queued data 221 * at the left window edge to the user. 222 * This is needed after the 3-WHS 223 * completes. 224 */ 225 goto present; /* ??? */ 226 } 227 m_adj(m, i); 228 *tlenp -= i; 229 th->th_seq += i; 230 } 231 } 232 tcpstat.tcps_rcvoopack++; 233 tcpstat.tcps_rcvoobyte += *tlenp; 234 235 /* 236 * While we overlap succeeding segments trim them or, 237 * if they are completely covered, dequeue them. 238 */ 239 while (q) { 240 register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; 241 if (i <= 0) 242 break; 243 if (i < q->tqe_len) { 244 q->tqe_th->th_seq += i; 245 q->tqe_len -= i; 246 m_adj(q->tqe_m, i); 247 break; 248 } 249 250 nq = LIST_NEXT(q, tqe_q); 251 LIST_REMOVE(q, tqe_q); 252 m_freem(q->tqe_m); 253 free(q, M_TSEGQ); 254 q = nq; 255 } 256 257 /* Insert the new segment queue entry into place. */ 258 te->tqe_m = m; 259 te->tqe_th = th; 260 te->tqe_len = *tlenp; 261 262 if (p == NULL) { 263 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); 264 } else { 265 LIST_INSERT_AFTER(p, te, tqe_q); 266 } 267 268 present: 269 /* 270 * Present data to user, advancing rcv_nxt through 271 * completed sequence space. 272 */ 273 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 274 return (0); 275 q = LIST_FIRST(&tp->t_segq); 276 if (!q || q->tqe_th->th_seq != tp->rcv_nxt) 277 return (0); 278 do { 279 tp->rcv_nxt += q->tqe_len; 280 flags = q->tqe_th->th_flags & TH_FIN; 281 nq = LIST_NEXT(q, tqe_q); 282 LIST_REMOVE(q, tqe_q); 283 if (so->so_state & SS_CANTRCVMORE) 284 m_freem(q->tqe_m); 285 else 286 sbappend(&so->so_rcv, q->tqe_m); 287 free(q, M_TSEGQ); 288 q = nq; 289 } while (q && q->tqe_th->th_seq == tp->rcv_nxt); 290 ND6_HINT(tp); 291 sorwakeup(so); 292 return (flags); 293 } 294 295 /* 296 * TCP input routine, follows pages 65-76 of the 297 * protocol specification dated September, 1981 very closely. 298 */ 299 #ifdef INET6 300 int 301 tcp6_input(mp, offp, proto) 302 struct mbuf **mp; 303 int *offp, proto; 304 { 305 register struct mbuf *m = *mp; 306 struct in6_ifaddr *ia6; 307 308 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 309 310 /* 311 * draft-itojun-ipv6-tcp-to-anycast 312 * better place to put this in? 313 */ 314 ia6 = ip6_getdstifaddr(m); 315 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 316 struct ip6_hdr *ip6; 317 318 ip6 = mtod(m, struct ip6_hdr *); 319 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 320 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 321 return IPPROTO_DONE; 322 } 323 324 tcp_input(m, *offp, proto); 325 return IPPROTO_DONE; 326 } 327 #endif 328 329 void 330 tcp_input(m, off0, proto) 331 register struct mbuf *m; 332 int off0, proto; 333 { 334 register struct tcphdr *th; 335 register struct ip *ip = NULL; 336 register struct ipovly *ipov; 337 register struct inpcb *inp = NULL; 338 u_char *optp = NULL; 339 int optlen = 0; 340 int len, tlen, off; 341 int drop_hdrlen; 342 register struct tcpcb *tp = NULL; 343 register int thflags; 344 struct socket *so = 0; 345 int todrop, acked, ourfinisacked, needoutput = 0; 346 u_long tiwin; 347 struct tcpopt to; /* options in this segment */ 348 struct rmxp_tao *taop; /* pointer to our TAO cache entry */ 349 struct rmxp_tao tao_noncached; /* in case there's no cached entry */ 350 struct sockaddr_in *next_hop = NULL; 351 int rstreason; /* For badport_bandlim accounting purposes */ 352 struct ip6_hdr *ip6 = NULL; 353 #ifdef INET6 354 int isipv6; 355 #else 356 const int isipv6 = 0; 357 #endif 358 #ifdef TCPDEBUG 359 short ostate = 0; 360 #endif 361 362 /* Grab info from MT_TAG mbufs prepended to the chain. */ 363 for (;m && m->m_type == MT_TAG; m = m->m_next) { 364 if (m->_m_tag_id == PACKET_TAG_IPFORWARD) 365 next_hop = (struct sockaddr_in *)m->m_hdr.mh_data; 366 } 367 #ifdef INET6 368 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 369 #endif 370 bzero((char *)&to, sizeof(to)); 371 372 tcpstat.tcps_rcvtotal++; 373 374 if (isipv6) { 375 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ 376 ip6 = mtod(m, struct ip6_hdr *); 377 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 378 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 379 tcpstat.tcps_rcvbadsum++; 380 goto drop; 381 } 382 th = (struct tcphdr *)((caddr_t)ip6 + off0); 383 384 /* 385 * Be proactive about unspecified IPv6 address in source. 386 * As we use all-zero to indicate unbounded/unconnected pcb, 387 * unspecified IPv6 address can be used to confuse us. 388 * 389 * Note that packets with unspecified IPv6 destination is 390 * already dropped in ip6_input. 391 */ 392 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 393 /* XXX stat */ 394 goto drop; 395 } 396 } else { 397 /* 398 * Get IP and TCP header together in first mbuf. 399 * Note: IP leaves IP header in first mbuf. 400 */ 401 if (off0 > sizeof(struct ip)) { 402 ip_stripoptions(m, (struct mbuf *)0); 403 off0 = sizeof(struct ip); 404 } 405 if (m->m_len < sizeof(struct tcpiphdr)) { 406 if ((m = m_pullup(m, sizeof(struct tcpiphdr))) == 0) { 407 tcpstat.tcps_rcvshort++; 408 return; 409 } 410 } 411 ip = mtod(m, struct ip *); 412 ipov = (struct ipovly *)ip; 413 th = (struct tcphdr *)((caddr_t)ip + off0); 414 tlen = ip->ip_len; 415 416 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 417 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 418 th->th_sum = m->m_pkthdr.csum_data; 419 else 420 th->th_sum = in_pseudo(ip->ip_src.s_addr, 421 ip->ip_dst.s_addr, 422 htonl(m->m_pkthdr.csum_data + 423 ip->ip_len + 424 IPPROTO_TCP)); 425 th->th_sum ^= 0xffff; 426 } else { 427 /* 428 * Checksum extended TCP header and data. 429 */ 430 len = sizeof(struct ip) + tlen; 431 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 432 ipov->ih_len = (u_short)tlen; 433 ipov->ih_len = htons(ipov->ih_len); 434 th->th_sum = in_cksum(m, len); 435 } 436 if (th->th_sum) { 437 tcpstat.tcps_rcvbadsum++; 438 goto drop; 439 } 440 #ifdef INET6 441 /* Re-initialization for later version check */ 442 ip->ip_v = IPVERSION; 443 #endif 444 } 445 446 /* 447 * Check that TCP offset makes sense, 448 * pull out TCP options and adjust length. XXX 449 */ 450 off = th->th_off << 2; 451 if (off < sizeof(struct tcphdr) || off > tlen) { 452 tcpstat.tcps_rcvbadoff++; 453 goto drop; 454 } 455 tlen -= off; /* tlen is used instead of ti->ti_len */ 456 if (off > sizeof(struct tcphdr)) { 457 if (isipv6) { 458 IP6_EXTHDR_CHECK(m, off0, off, ); 459 ip6 = mtod(m, struct ip6_hdr *); 460 th = (struct tcphdr *)((caddr_t)ip6 + off0); 461 } else { 462 if (m->m_len < sizeof(struct ip) + off) { 463 if ((m = m_pullup(m, sizeof(struct ip) + off)) 464 == 0) { 465 tcpstat.tcps_rcvshort++; 466 return; 467 } 468 ip = mtod(m, struct ip *); 469 ipov = (struct ipovly *)ip; 470 th = (struct tcphdr *)((caddr_t)ip + off0); 471 } 472 } 473 optlen = off - sizeof(struct tcphdr); 474 optp = (u_char *)(th + 1); 475 } 476 thflags = th->th_flags; 477 478 #ifdef TCP_DROP_SYNFIN 479 /* 480 * If the drop_synfin option is enabled, drop all packets with 481 * both the SYN and FIN bits set. This prevents e.g. nmap from 482 * identifying the TCP/IP stack. 483 * 484 * This is a violation of the TCP specification. 485 */ 486 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN)) 487 goto drop; 488 #endif 489 490 /* 491 * Convert TCP protocol specific fields to host format. 492 */ 493 th->th_seq = ntohl(th->th_seq); 494 th->th_ack = ntohl(th->th_ack); 495 th->th_win = ntohs(th->th_win); 496 th->th_urp = ntohs(th->th_urp); 497 498 /* 499 * Delay droping TCP, IP headers, IPv6 ext headers, and TCP options, 500 * until after ip6_savecontrol() is called and before other functions 501 * which don't want those proto headers. 502 * Because ip6_savecontrol() is going to parse the mbuf to 503 * search for data to be passed up to user-land, it wants mbuf 504 * parameters to be unchanged. 505 * XXX: the call of ip6_savecontrol() has been obsoleted based on 506 * latest version of the advanced API (20020110). 507 */ 508 drop_hdrlen = off0 + off; 509 510 /* 511 * Locate pcb for segment. 512 */ 513 findpcb: 514 /* IPFIREWALL_FORWARD section */ 515 if (next_hop != NULL && isipv6 == 0) { /* IPv6 support is not yet */ 516 /* 517 * Transparently forwarded. Pretend to be the destination. 518 * already got one like this? 519 */ 520 inp = in_pcblookup_hash(&tcbinfo, ip->ip_src, th->th_sport, 521 ip->ip_dst, th->th_dport, 522 0, m->m_pkthdr.rcvif); 523 if (!inp) { 524 /* It's new. Try find the ambushing socket. */ 525 inp = in_pcblookup_hash(&tcbinfo, 526 ip->ip_src, th->th_sport, 527 next_hop->sin_addr, 528 next_hop->sin_port ? 529 ntohs(next_hop->sin_port) : 530 th->th_dport, 531 1, m->m_pkthdr.rcvif); 532 } 533 } else { 534 if (isipv6) 535 inp = in6_pcblookup_hash(&tcbinfo, 536 &ip6->ip6_src, th->th_sport, 537 &ip6->ip6_dst, th->th_dport, 538 1, m->m_pkthdr.rcvif); 539 else 540 inp = in_pcblookup_hash(&tcbinfo, 541 ip->ip_src, th->th_sport, 542 ip->ip_dst, th->th_dport, 543 1, m->m_pkthdr.rcvif); 544 } 545 546 #ifdef IPSEC 547 if (isipv6) { 548 if (inp != NULL && ipsec6_in_reject_so(m, inp->inp_socket)) { 549 ipsec6stat.in_polvio++; 550 goto drop; 551 } 552 } else { 553 if (inp != NULL && ipsec4_in_reject_so(m, inp->inp_socket)) { 554 ipsecstat.in_polvio++; 555 goto drop; 556 } 557 } 558 #endif 559 #ifdef FAST_IPSEC 560 if (isipv6) { 561 if (inp != NULL && ipsec6_in_reject(m, inp)) { 562 goto drop; 563 } 564 } else { 565 if (inp != NULL && ipsec4_in_reject(m, inp)) { 566 goto drop; 567 } 568 } 569 #endif 570 571 /* 572 * If the state is CLOSED (i.e., TCB does not exist) then 573 * all data in the incoming segment is discarded. 574 * If the TCB exists but is in CLOSED state, it is embryonic, 575 * but should either do a listen or a connect soon. 576 */ 577 if (inp == NULL) { 578 if (log_in_vain) { 579 #ifdef INET6 580 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; 581 #else 582 char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"]; 583 #endif 584 if (isipv6) { 585 strcpy(dbuf, "["); 586 strcpy(sbuf, "["); 587 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); 588 strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); 589 strcat(dbuf, "]"); 590 strcat(sbuf, "]"); 591 } else { 592 strcpy(dbuf, inet_ntoa(ip->ip_dst)); 593 strcpy(sbuf, inet_ntoa(ip->ip_src)); 594 } 595 switch (log_in_vain) { 596 case 1: 597 if ((thflags & TH_SYN) == 0) 598 break; 599 case 2: 600 log(LOG_INFO, 601 "Connection attempt to TCP %s:%d " 602 "from %s:%d flags:0x%02x\n", 603 dbuf, ntohs(th->th_dport), sbuf, 604 ntohs(th->th_sport), thflags); 605 break; 606 default: 607 break; 608 } 609 } 610 if (blackhole) { 611 switch (blackhole) { 612 case 1: 613 if (thflags & TH_SYN) 614 goto drop; 615 break; 616 case 2: 617 goto drop; 618 default: 619 goto drop; 620 } 621 } 622 rstreason = BANDLIM_RST_CLOSEDPORT; 623 goto dropwithreset; 624 } 625 tp = intotcpcb(inp); 626 if (tp == NULL) { 627 rstreason = BANDLIM_RST_CLOSEDPORT; 628 goto dropwithreset; 629 } 630 if (tp->t_state == TCPS_CLOSED) 631 goto drop; 632 633 /* Unscale the window into a 32-bit value. */ 634 if ((thflags & TH_SYN) == 0) 635 tiwin = th->th_win << tp->snd_scale; 636 else 637 tiwin = th->th_win; 638 639 so = inp->inp_socket; 640 if (so->so_options & (SO_DEBUG|SO_ACCEPTCONN)) { 641 struct in_conninfo inc; 642 #ifdef TCPDEBUG 643 if (so->so_options & SO_DEBUG) { 644 ostate = tp->t_state; 645 if (isipv6) 646 bcopy((char *)ip6, (char *)tcp_saveipgen, 647 sizeof(*ip6)); 648 else 649 bcopy((char *)ip, (char *)tcp_saveipgen, 650 sizeof(*ip)); 651 tcp_savetcp = *th; 652 } 653 #endif 654 /* skip if this isn't a listen socket */ 655 if ((so->so_options & SO_ACCEPTCONN) == 0) 656 goto after_listen; 657 #ifdef INET6 658 inc.inc_isipv6 = isipv6; 659 #endif 660 if (isipv6) { 661 inc.inc6_faddr = ip6->ip6_src; 662 inc.inc6_laddr = ip6->ip6_dst; 663 inc.inc6_route.ro_rt = NULL; /* XXX */ 664 } else { 665 inc.inc_faddr = ip->ip_src; 666 inc.inc_laddr = ip->ip_dst; 667 inc.inc_route.ro_rt = NULL; /* XXX */ 668 } 669 inc.inc_fport = th->th_sport; 670 inc.inc_lport = th->th_dport; 671 672 /* 673 * If the state is LISTEN then ignore segment if it contains 674 * a RST. If the segment contains an ACK then it is bad and 675 * send a RST. If it does not contain a SYN then it is not 676 * interesting; drop it. 677 * 678 * If the state is SYN_RECEIVED (syncache) and seg contains 679 * an ACK, but not for our SYN/ACK, send a RST. If the seg 680 * contains a RST, check the sequence number to see if it 681 * is a valid reset segment. 682 */ 683 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 684 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 685 if (!syncache_expand(&inc, th, &so, m)) { 686 /* 687 * No syncache entry, or ACK was not 688 * for our SYN/ACK. Send a RST. 689 */ 690 tcpstat.tcps_badsyn++; 691 rstreason = BANDLIM_RST_OPENPORT; 692 goto dropwithreset; 693 } 694 if (so == NULL) 695 /* 696 * Could not complete 3-way handshake, 697 * connection is being closed down, and 698 * syncache will free mbuf. 699 */ 700 return; 701 /* 702 * Socket is created in state SYN_RECEIVED. 703 * Continue processing segment. 704 */ 705 inp = sotoinpcb(so); 706 tp = intotcpcb(inp); 707 /* 708 * This is what would have happened in 709 * tcp_output() when the SYN,ACK was sent. 710 */ 711 tp->snd_up = tp->snd_una; 712 tp->snd_max = tp->snd_nxt = tp->iss + 1; 713 tp->last_ack_sent = tp->rcv_nxt; 714 /* 715 * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled 716 * until the _second_ ACK is received: 717 * rcv SYN (set wscale opts) --> send SYN/ACK, set snd_wnd = window. 718 * rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale, 719 * move to ESTAB, set snd_wnd to tiwin. 720 */ 721 tp->snd_wnd = tiwin; /* unscaled */ 722 goto after_listen; 723 } 724 if (thflags & TH_RST) { 725 syncache_chkrst(&inc, th); 726 goto drop; 727 } 728 if (thflags & TH_ACK) { 729 syncache_badack(&inc); 730 tcpstat.tcps_badsyn++; 731 rstreason = BANDLIM_RST_OPENPORT; 732 goto dropwithreset; 733 } 734 goto drop; 735 } 736 737 /* 738 * Segment's flags are (SYN) or (SYN|FIN). 739 */ 740 #ifdef INET6 741 /* 742 * If deprecated address is forbidden, 743 * we do not accept SYN to deprecated interface 744 * address to prevent any new inbound connection from 745 * getting established. 746 * When we do not accept SYN, we send a TCP RST, 747 * with deprecated source address (instead of dropping 748 * it). We compromise it as it is much better for peer 749 * to send a RST, and RST will be the final packet 750 * for the exchange. 751 * 752 * If we do not forbid deprecated addresses, we accept 753 * the SYN packet. RFC2462 does not suggest dropping 754 * SYN in this case. 755 * If we decipher RFC2462 5.5.4, it says like this: 756 * 1. use of deprecated addr with existing 757 * communication is okay - "SHOULD continue to be 758 * used" 759 * 2. use of it with new communication: 760 * (2a) "SHOULD NOT be used if alternate address 761 * with sufficient scope is available" 762 * (2b) nothing mentioned otherwise. 763 * Here we fall into (2b) case as we have no choice in 764 * our source address selection - we must obey the peer. 765 * 766 * The wording in RFC2462 is confusing, and there are 767 * multiple description text for deprecated address 768 * handling - worse, they are not exactly the same. 769 * I believe 5.5.4 is the best one, so we follow 5.5.4. 770 */ 771 if (isipv6 && !ip6_use_deprecated) { 772 struct in6_ifaddr *ia6; 773 774 if ((ia6 = ip6_getdstifaddr(m)) && 775 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 776 tp = NULL; 777 rstreason = BANDLIM_RST_OPENPORT; 778 goto dropwithreset; 779 } 780 } 781 #endif 782 /* 783 * If it is from this socket, drop it, it must be forged. 784 * Don't bother responding if the destination was a broadcast. 785 */ 786 if (th->th_dport == th->th_sport) { 787 if (isipv6) { 788 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, 789 &ip6->ip6_src)) 790 goto drop; 791 } else { 792 if (ip->ip_dst.s_addr == ip->ip_src.s_addr) 793 goto drop; 794 } 795 } 796 /* 797 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 798 * 799 * Note that it is quite possible to receive unicast 800 * link-layer packets with a broadcast IP address. Use 801 * in_broadcast() to find them. 802 */ 803 if (m->m_flags & (M_BCAST|M_MCAST)) 804 goto drop; 805 if (isipv6) { 806 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 807 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 808 goto drop; 809 } else { 810 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 811 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 812 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 813 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 814 goto drop; 815 } 816 /* 817 * SYN appears to be valid; create compressed TCP state 818 * for syncache, or perform t/tcp connection. 819 */ 820 if (so->so_qlen <= so->so_qlimit) { 821 tcp_dooptions(&to, optp, optlen, 1); 822 if (!syncache_add(&inc, &to, th, &so, m)) 823 goto drop; 824 if (so == NULL) 825 /* 826 * Entry added to syncache, mbuf used to 827 * send SYN,ACK packet. 828 */ 829 return; 830 /* 831 * Segment passed TAO tests. 832 */ 833 inp = sotoinpcb(so); 834 tp = intotcpcb(inp); 835 tp->snd_wnd = tiwin; 836 tp->t_starttime = ticks; 837 tp->t_state = TCPS_ESTABLISHED; 838 839 /* 840 * If there is a FIN, or if there is data and the 841 * connection is local, then delay SYN,ACK(SYN) in 842 * the hope of piggy-backing it on a response 843 * segment. Otherwise must send ACK now in case 844 * the other side is slow starting. 845 */ 846 if (DELAY_ACK(tp) && 847 ((thflags & TH_FIN) || 848 (tlen != 0 && 849 ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 850 (!isipv6 && in_localaddr(inp->inp_faddr)))))) { 851 callout_reset(tp->tt_delack, tcp_delacktime, 852 tcp_timer_delack, tp); 853 tp->t_flags |= TF_NEEDSYN; 854 } else 855 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 856 857 tcpstat.tcps_connects++; 858 soisconnected(so); 859 goto trimthenstep6; 860 } 861 goto drop; 862 } 863 after_listen: 864 865 /* XXX temp debugging */ 866 /* should not happen - syncache should pick up these connections */ 867 if (tp->t_state == TCPS_LISTEN) 868 panic("tcp_input: TCPS_LISTEN"); 869 870 /* 871 * Segment received on connection. 872 * Reset idle time and keep-alive timer. 873 */ 874 tp->t_rcvtime = ticks; 875 if (TCPS_HAVEESTABLISHED(tp->t_state)) 876 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 877 878 /* 879 * Process options. 880 * XXX this is tradtitional behavior, may need to be cleaned up. 881 */ 882 tcp_dooptions(&to, optp, optlen, thflags & TH_SYN); 883 if (thflags & TH_SYN) { 884 if (to.to_flags & TOF_SCALE) { 885 tp->t_flags |= TF_RCVD_SCALE; 886 tp->requested_s_scale = to.to_requested_s_scale; 887 } 888 if (to.to_flags & TOF_TS) { 889 tp->t_flags |= TF_RCVD_TSTMP; 890 tp->ts_recent = to.to_tsval; 891 tp->ts_recent_age = ticks; 892 } 893 if (to.to_flags & (TOF_CC|TOF_CCNEW)) 894 tp->t_flags |= TF_RCVD_CC; 895 if (to.to_flags & TOF_MSS) 896 tcp_mss(tp, to.to_mss); 897 } 898 899 /* 900 * Header prediction: check for the two common cases 901 * of a uni-directional data xfer. If the packet has 902 * no control flags, is in-sequence, the window didn't 903 * change and we're not retransmitting, it's a 904 * candidate. If the length is zero and the ack moved 905 * forward, we're the sender side of the xfer. Just 906 * free the data acked & wake any higher level process 907 * that was blocked waiting for space. If the length 908 * is non-zero and the ack didn't move, we're the 909 * receiver side. If we're getting packets in-order 910 * (the reassembly queue is empty), add the data to 911 * the socket buffer and note that we need a delayed ack. 912 * Make sure that the hidden state-flags are also off. 913 * Since we check for TCPS_ESTABLISHED above, it can only 914 * be TH_NEEDSYN. 915 */ 916 if (tp->t_state == TCPS_ESTABLISHED && 917 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 918 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 919 ((to.to_flags & TOF_TS) == 0 || 920 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 921 /* 922 * Using the CC option is compulsory if once started: 923 * the segment is OK if no T/TCP was negotiated or 924 * if the segment has a CC option equal to CCrecv 925 */ 926 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) || 927 ((to.to_flags & TOF_CC) != 0 && to.to_cc == tp->cc_recv)) && 928 th->th_seq == tp->rcv_nxt && 929 tiwin && tiwin == tp->snd_wnd && 930 tp->snd_nxt == tp->snd_max) { 931 932 /* 933 * If last ACK falls within this segment's sequence numbers, 934 * record the timestamp. 935 * NOTE that the test is modified according to the latest 936 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 937 */ 938 if ((to.to_flags & TOF_TS) != 0 && 939 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 940 tp->ts_recent_age = ticks; 941 tp->ts_recent = to.to_tsval; 942 } 943 944 if (tlen == 0) { 945 if (SEQ_GT(th->th_ack, tp->snd_una) && 946 SEQ_LEQ(th->th_ack, tp->snd_max) && 947 tp->snd_cwnd >= tp->snd_wnd && 948 ((!tcp_do_newreno && 949 tp->t_dupacks < tcprexmtthresh) || 950 (tcp_do_newreno && 951 !SEQ_LT(tp->snd_una, tp->snd_recover)))) { 952 /* 953 * this is a pure ack for outstanding data. 954 */ 955 ++tcpstat.tcps_predack; 956 /* 957 * "bad retransmit" recovery 958 */ 959 if (tp->t_rxtshift == 1 && 960 ticks < tp->t_badrxtwin) { 961 tp->snd_cwnd = tp->snd_cwnd_prev; 962 tp->snd_ssthresh = 963 tp->snd_ssthresh_prev; 964 tp->snd_high = tp->snd_high_prev; 965 tp->snd_nxt = tp->snd_max; 966 tp->t_badrxtwin = 0; 967 } 968 /* 969 * Recalculate the retransmit timer / rtt. 970 * 971 * Some machines (certain windows boxes) 972 * send broken timestamp replies during the 973 * SYN+ACK phase, ignore timestamps of 0. 974 */ 975 if ((to.to_flags & TOF_TS) != 0 && 976 to.to_tsecr) { 977 tcp_xmit_timer(tp, 978 ticks - to.to_tsecr + 1); 979 } else if (tp->t_rtttime && 980 SEQ_GT(th->th_ack, tp->t_rtseq)) { 981 tcp_xmit_timer(tp, 982 ticks - tp->t_rtttime); 983 } 984 tcp_xmit_bandwidth_limit(tp, th->th_ack); 985 acked = th->th_ack - tp->snd_una; 986 tcpstat.tcps_rcvackpack++; 987 tcpstat.tcps_rcvackbyte += acked; 988 sbdrop(&so->so_snd, acked); 989 if (SEQ_GT(tp->snd_una, tp->snd_high) && 990 SEQ_LEQ(th->th_ack, tp->snd_high)) 991 tp->snd_high = th->th_ack - 1; 992 tp->snd_una = tp->snd_recover = th->th_ack; 993 tp->t_dupacks = 0; 994 m_freem(m); 995 ND6_HINT(tp); /* some progress has been done */ 996 997 /* 998 * If all outstanding data are acked, stop 999 * retransmit timer, otherwise restart timer 1000 * using current (possibly backed-off) value. 1001 * If process is waiting for space, 1002 * wakeup/selwakeup/signal. If data 1003 * are ready to send, let tcp_output 1004 * decide between more output or persist. 1005 */ 1006 if (tp->snd_una == tp->snd_max) 1007 callout_stop(tp->tt_rexmt); 1008 else if (!callout_active(tp->tt_persist)) 1009 callout_reset(tp->tt_rexmt, 1010 tp->t_rxtcur, 1011 tcp_timer_rexmt, tp); 1012 1013 sowwakeup(so); 1014 if (so->so_snd.sb_cc) 1015 (void) tcp_output(tp); 1016 return; 1017 } 1018 } else if (th->th_ack == tp->snd_una && 1019 LIST_EMPTY(&tp->t_segq) && 1020 tlen <= sbspace(&so->so_rcv)) { 1021 /* 1022 * this is a pure, in-sequence data packet 1023 * with nothing on the reassembly queue and 1024 * we have enough buffer space to take it. 1025 */ 1026 ++tcpstat.tcps_preddat; 1027 tp->rcv_nxt += tlen; 1028 tcpstat.tcps_rcvpack++; 1029 tcpstat.tcps_rcvbyte += tlen; 1030 ND6_HINT(tp); /* some progress has been done */ 1031 /* 1032 * Add data to socket buffer. 1033 */ 1034 if (so->so_state & SS_CANTRCVMORE) { 1035 m_freem(m); 1036 } else { 1037 m_adj(m, drop_hdrlen); /* delayed header drop */ 1038 sbappend(&so->so_rcv, m); 1039 } 1040 sorwakeup(so); 1041 if (DELAY_ACK(tp)) { 1042 callout_reset(tp->tt_delack, tcp_delacktime, 1043 tcp_timer_delack, tp); 1044 } else { 1045 tp->t_flags |= TF_ACKNOW; 1046 tcp_output(tp); 1047 } 1048 return; 1049 } 1050 } 1051 1052 /* 1053 * Calculate amount of space in receive window, 1054 * and then do TCP input processing. 1055 * Receive window is amount of space in rcv queue, 1056 * but not less than advertised window. 1057 */ 1058 { int win; 1059 1060 win = sbspace(&so->so_rcv); 1061 if (win < 0) 1062 win = 0; 1063 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1064 } 1065 1066 switch (tp->t_state) { 1067 1068 /* 1069 * If the state is SYN_RECEIVED: 1070 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1071 */ 1072 case TCPS_SYN_RECEIVED: 1073 if ((thflags & TH_ACK) && 1074 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1075 SEQ_GT(th->th_ack, tp->snd_max))) { 1076 rstreason = BANDLIM_RST_OPENPORT; 1077 goto dropwithreset; 1078 } 1079 break; 1080 1081 /* 1082 * If the state is SYN_SENT: 1083 * if seg contains an ACK, but not for our SYN, drop the input. 1084 * if seg contains a RST, then drop the connection. 1085 * if seg does not contain SYN, then drop it. 1086 * Otherwise this is an acceptable SYN segment 1087 * initialize tp->rcv_nxt and tp->irs 1088 * if seg contains ack then advance tp->snd_una 1089 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1090 * arrange for segment to be acked (eventually) 1091 * continue processing rest of data/controls, beginning with URG 1092 */ 1093 case TCPS_SYN_SENT: 1094 if ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL) { 1095 taop = &tao_noncached; 1096 bzero(taop, sizeof(*taop)); 1097 } 1098 1099 if ((thflags & TH_ACK) && 1100 (SEQ_LEQ(th->th_ack, tp->iss) || 1101 SEQ_GT(th->th_ack, tp->snd_max))) { 1102 /* 1103 * If we have a cached CCsent for the remote host, 1104 * hence we haven't just crashed and restarted, 1105 * do not send a RST. This may be a retransmission 1106 * from the other side after our earlier ACK was lost. 1107 * Our new SYN, when it arrives, will serve as the 1108 * needed ACK. 1109 */ 1110 if (taop->tao_ccsent != 0) 1111 goto drop; 1112 else { 1113 rstreason = BANDLIM_UNLIMITED; 1114 goto dropwithreset; 1115 } 1116 } 1117 if (thflags & TH_RST) { 1118 if (thflags & TH_ACK) 1119 tp = tcp_drop(tp, ECONNREFUSED); 1120 goto drop; 1121 } 1122 if ((thflags & TH_SYN) == 0) 1123 goto drop; 1124 tp->snd_wnd = th->th_win; /* initial send window */ 1125 tp->cc_recv = to.to_cc; /* foreign CC */ 1126 1127 tp->irs = th->th_seq; 1128 tcp_rcvseqinit(tp); 1129 if (thflags & TH_ACK) { 1130 /* 1131 * Our SYN was acked. If segment contains CC.ECHO 1132 * option, check it to make sure this segment really 1133 * matches our SYN. If not, just drop it as old 1134 * duplicate, but send an RST if we're still playing 1135 * by the old rules. If no CC.ECHO option, make sure 1136 * we don't get fooled into using T/TCP. 1137 */ 1138 if (to.to_flags & TOF_CCECHO) { 1139 if (tp->cc_send != to.to_ccecho) { 1140 if (taop->tao_ccsent != 0) 1141 goto drop; 1142 else { 1143 rstreason = BANDLIM_UNLIMITED; 1144 goto dropwithreset; 1145 } 1146 } 1147 } else 1148 tp->t_flags &= ~TF_RCVD_CC; 1149 tcpstat.tcps_connects++; 1150 soisconnected(so); 1151 /* Do window scaling on this connection? */ 1152 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1153 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1154 tp->snd_scale = tp->requested_s_scale; 1155 tp->rcv_scale = tp->request_r_scale; 1156 } 1157 /* Segment is acceptable, update cache if undefined. */ 1158 if (taop->tao_ccsent == 0) 1159 taop->tao_ccsent = to.to_ccecho; 1160 1161 tp->rcv_adv += tp->rcv_wnd; 1162 tp->snd_una++; /* SYN is acked */ 1163 /* 1164 * If there's data, delay ACK; if there's also a FIN 1165 * ACKNOW will be turned on later. 1166 */ 1167 if (DELAY_ACK(tp) && tlen != 0) 1168 callout_reset(tp->tt_delack, tcp_delacktime, 1169 tcp_timer_delack, tp); 1170 else 1171 tp->t_flags |= TF_ACKNOW; 1172 /* 1173 * Received <SYN,ACK> in SYN_SENT[*] state. 1174 * Transitions: 1175 * SYN_SENT --> ESTABLISHED 1176 * SYN_SENT* --> FIN_WAIT_1 1177 */ 1178 tp->t_starttime = ticks; 1179 if (tp->t_flags & TF_NEEDFIN) { 1180 tp->t_state = TCPS_FIN_WAIT_1; 1181 tp->t_flags &= ~TF_NEEDFIN; 1182 thflags &= ~TH_SYN; 1183 } else { 1184 tp->t_state = TCPS_ESTABLISHED; 1185 callout_reset(tp->tt_keep, tcp_keepidle, 1186 tcp_timer_keep, tp); 1187 } 1188 } else { 1189 /* 1190 * Received initial SYN in SYN-SENT[*] state => 1191 * simultaneous open. If segment contains CC option 1192 * and there is a cached CC, apply TAO test. 1193 * If it succeeds, connection is * half-synchronized. 1194 * Otherwise, do 3-way handshake: 1195 * SYN-SENT -> SYN-RECEIVED 1196 * SYN-SENT* -> SYN-RECEIVED* 1197 * If there was no CC option, clear cached CC value. 1198 */ 1199 tp->t_flags |= TF_ACKNOW; 1200 callout_stop(tp->tt_rexmt); 1201 if (to.to_flags & TOF_CC) { 1202 if (taop->tao_cc != 0 && 1203 CC_GT(to.to_cc, taop->tao_cc)) { 1204 /* 1205 * update cache and make transition: 1206 * SYN-SENT -> ESTABLISHED* 1207 * SYN-SENT* -> FIN-WAIT-1* 1208 */ 1209 taop->tao_cc = to.to_cc; 1210 tp->t_starttime = ticks; 1211 if (tp->t_flags & TF_NEEDFIN) { 1212 tp->t_state = TCPS_FIN_WAIT_1; 1213 tp->t_flags &= ~TF_NEEDFIN; 1214 } else { 1215 tp->t_state = TCPS_ESTABLISHED; 1216 callout_reset(tp->tt_keep, 1217 tcp_keepidle, 1218 tcp_timer_keep, 1219 tp); 1220 } 1221 tp->t_flags |= TF_NEEDSYN; 1222 } else 1223 tp->t_state = TCPS_SYN_RECEIVED; 1224 } else { 1225 /* CC.NEW or no option => invalidate cache */ 1226 taop->tao_cc = 0; 1227 tp->t_state = TCPS_SYN_RECEIVED; 1228 } 1229 } 1230 1231 trimthenstep6: 1232 /* 1233 * Advance th->th_seq to correspond to first data byte. 1234 * If data, trim to stay within window, 1235 * dropping FIN if necessary. 1236 */ 1237 th->th_seq++; 1238 if (tlen > tp->rcv_wnd) { 1239 todrop = tlen - tp->rcv_wnd; 1240 m_adj(m, -todrop); 1241 tlen = tp->rcv_wnd; 1242 thflags &= ~TH_FIN; 1243 tcpstat.tcps_rcvpackafterwin++; 1244 tcpstat.tcps_rcvbyteafterwin += todrop; 1245 } 1246 tp->snd_wl1 = th->th_seq - 1; 1247 tp->rcv_up = th->th_seq; 1248 /* 1249 * Client side of transaction: already sent SYN and data. 1250 * If the remote host used T/TCP to validate the SYN, 1251 * our data will be ACK'd; if so, enter normal data segment 1252 * processing in the middle of step 5, ack processing. 1253 * Otherwise, goto step 6. 1254 */ 1255 if (thflags & TH_ACK) 1256 goto process_ACK; 1257 1258 goto step6; 1259 1260 /* 1261 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1262 * if segment contains a SYN and CC [not CC.NEW] option: 1263 * if state == TIME_WAIT and connection duration > MSL, 1264 * drop packet and send RST; 1265 * 1266 * if SEG.CC > CCrecv then is new SYN, and can implicitly 1267 * ack the FIN (and data) in retransmission queue. 1268 * Complete close and delete TCPCB. Then reprocess 1269 * segment, hoping to find new TCPCB in LISTEN state; 1270 * 1271 * else must be old SYN; drop it. 1272 * else do normal processing. 1273 */ 1274 case TCPS_LAST_ACK: 1275 case TCPS_CLOSING: 1276 case TCPS_TIME_WAIT: 1277 if ((thflags & TH_SYN) && 1278 (to.to_flags & TOF_CC) && tp->cc_recv != 0) { 1279 if (tp->t_state == TCPS_TIME_WAIT && 1280 (ticks - tp->t_starttime) > tcp_msl) { 1281 rstreason = BANDLIM_UNLIMITED; 1282 goto dropwithreset; 1283 } 1284 if (CC_GT(to.to_cc, tp->cc_recv)) { 1285 tp = tcp_close(tp); 1286 goto findpcb; 1287 } 1288 else 1289 goto drop; 1290 } 1291 break; /* continue normal processing */ 1292 } 1293 1294 /* 1295 * States other than LISTEN or SYN_SENT. 1296 * First check the RST flag and sequence number since reset segments 1297 * are exempt from the timestamp and connection count tests. This 1298 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1299 * below which allowed reset segments in half the sequence space 1300 * to fall though and be processed (which gives forged reset 1301 * segments with a random sequence number a 50 percent chance of 1302 * killing a connection). 1303 * Then check timestamp, if present. 1304 * Then check the connection count, if present. 1305 * Then check that at least some bytes of segment are within 1306 * receive window. If segment begins before rcv_nxt, 1307 * drop leading data (and SYN); if nothing left, just ack. 1308 * 1309 * 1310 * If the RST bit is set, check the sequence number to see 1311 * if this is a valid reset segment. 1312 * RFC 793 page 37: 1313 * In all states except SYN-SENT, all reset (RST) segments 1314 * are validated by checking their SEQ-fields. A reset is 1315 * valid if its sequence number is in the window. 1316 * Note: this does not take into account delayed ACKs, so 1317 * we should test against last_ack_sent instead of rcv_nxt. 1318 * The sequence number in the reset segment is normally an 1319 * echo of our outgoing acknowlegement numbers, but some hosts 1320 * send a reset with the sequence number at the rightmost edge 1321 * of our receive window, and we have to handle this case. 1322 * If we have multiple segments in flight, the intial reset 1323 * segment sequence numbers will be to the left of last_ack_sent, 1324 * but they will eventually catch up. 1325 * In any case, it never made sense to trim reset segments to 1326 * fit the receive window since RFC 1122 says: 1327 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1328 * 1329 * A TCP SHOULD allow a received RST segment to include data. 1330 * 1331 * DISCUSSION 1332 * It has been suggested that a RST segment could contain 1333 * ASCII text that encoded and explained the cause of the 1334 * RST. No standard has yet been established for such 1335 * data. 1336 * 1337 * If the reset segment passes the sequence number test examine 1338 * the state: 1339 * SYN_RECEIVED STATE: 1340 * If passive open, return to LISTEN state. 1341 * If active open, inform user that connection was refused. 1342 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1343 * Inform user that connection was reset, and close tcb. 1344 * CLOSING, LAST_ACK STATES: 1345 * Close the tcb. 1346 * TIME_WAIT STATE: 1347 * Drop the segment - see Stevens, vol. 2, p. 964 and 1348 * RFC 1337. 1349 */ 1350 if (thflags & TH_RST) { 1351 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 1352 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1353 switch (tp->t_state) { 1354 1355 case TCPS_SYN_RECEIVED: 1356 so->so_error = ECONNREFUSED; 1357 goto close; 1358 1359 case TCPS_ESTABLISHED: 1360 case TCPS_FIN_WAIT_1: 1361 case TCPS_FIN_WAIT_2: 1362 case TCPS_CLOSE_WAIT: 1363 so->so_error = ECONNRESET; 1364 close: 1365 tp->t_state = TCPS_CLOSED; 1366 tcpstat.tcps_drops++; 1367 tp = tcp_close(tp); 1368 break; 1369 1370 case TCPS_CLOSING: 1371 case TCPS_LAST_ACK: 1372 tp = tcp_close(tp); 1373 break; 1374 1375 case TCPS_TIME_WAIT: 1376 break; 1377 } 1378 } 1379 goto drop; 1380 } 1381 1382 /* 1383 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1384 * and it's less than ts_recent, drop it. 1385 */ 1386 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 1387 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1388 1389 /* Check to see if ts_recent is over 24 days old. */ 1390 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1391 /* 1392 * Invalidate ts_recent. If this segment updates 1393 * ts_recent, the age will be reset later and ts_recent 1394 * will get a valid value. If it does not, setting 1395 * ts_recent to zero will at least satisfy the 1396 * requirement that zero be placed in the timestamp 1397 * echo reply when ts_recent isn't valid. The 1398 * age isn't reset until we get a valid ts_recent 1399 * because we don't want out-of-order segments to be 1400 * dropped when ts_recent is old. 1401 */ 1402 tp->ts_recent = 0; 1403 } else { 1404 tcpstat.tcps_rcvduppack++; 1405 tcpstat.tcps_rcvdupbyte += tlen; 1406 tcpstat.tcps_pawsdrop++; 1407 if (tlen) 1408 goto dropafterack; 1409 goto drop; 1410 } 1411 } 1412 1413 /* 1414 * T/TCP mechanism 1415 * If T/TCP was negotiated and the segment doesn't have CC, 1416 * or if its CC is wrong then drop the segment. 1417 * RST segments do not have to comply with this. 1418 */ 1419 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) && 1420 ((to.to_flags & TOF_CC) == 0 || tp->cc_recv != to.to_cc)) 1421 goto dropafterack; 1422 1423 /* 1424 * In the SYN-RECEIVED state, validate that the packet belongs to 1425 * this connection before trimming the data to fit the receive 1426 * window. Check the sequence number versus IRS since we know 1427 * the sequence numbers haven't wrapped. This is a partial fix 1428 * for the "LAND" DoS attack. 1429 */ 1430 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1431 rstreason = BANDLIM_RST_OPENPORT; 1432 goto dropwithreset; 1433 } 1434 1435 todrop = tp->rcv_nxt - th->th_seq; 1436 if (todrop > 0) { 1437 if (thflags & TH_SYN) { 1438 thflags &= ~TH_SYN; 1439 th->th_seq++; 1440 if (th->th_urp > 1) 1441 th->th_urp--; 1442 else 1443 thflags &= ~TH_URG; 1444 todrop--; 1445 } 1446 /* 1447 * Following if statement from Stevens, vol. 2, p. 960. 1448 */ 1449 if (todrop > tlen 1450 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 1451 /* 1452 * Any valid FIN must be to the left of the window. 1453 * At this point the FIN must be a duplicate or out 1454 * of sequence; drop it. 1455 */ 1456 thflags &= ~TH_FIN; 1457 1458 /* 1459 * Send an ACK to resynchronize and drop any data. 1460 * But keep on processing for RST or ACK. 1461 */ 1462 tp->t_flags |= TF_ACKNOW; 1463 todrop = tlen; 1464 tcpstat.tcps_rcvduppack++; 1465 tcpstat.tcps_rcvdupbyte += todrop; 1466 } else { 1467 tcpstat.tcps_rcvpartduppack++; 1468 tcpstat.tcps_rcvpartdupbyte += todrop; 1469 } 1470 drop_hdrlen += todrop; /* drop from the top afterwards */ 1471 th->th_seq += todrop; 1472 tlen -= todrop; 1473 if (th->th_urp > todrop) 1474 th->th_urp -= todrop; 1475 else { 1476 thflags &= ~TH_URG; 1477 th->th_urp = 0; 1478 } 1479 } 1480 1481 /* 1482 * If new data are received on a connection after the 1483 * user processes are gone, then RST the other end. 1484 */ 1485 if ((so->so_state & SS_NOFDREF) && 1486 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1487 tp = tcp_close(tp); 1488 tcpstat.tcps_rcvafterclose++; 1489 rstreason = BANDLIM_UNLIMITED; 1490 goto dropwithreset; 1491 } 1492 1493 /* 1494 * If segment ends after window, drop trailing data 1495 * (and PUSH and FIN); if nothing left, just ACK. 1496 */ 1497 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd); 1498 if (todrop > 0) { 1499 tcpstat.tcps_rcvpackafterwin++; 1500 if (todrop >= tlen) { 1501 tcpstat.tcps_rcvbyteafterwin += tlen; 1502 /* 1503 * If a new connection request is received 1504 * while in TIME_WAIT, drop the old connection 1505 * and start over if the sequence numbers 1506 * are above the previous ones. 1507 */ 1508 if (thflags & TH_SYN && 1509 tp->t_state == TCPS_TIME_WAIT && 1510 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 1511 tp = tcp_close(tp); 1512 goto findpcb; 1513 } 1514 /* 1515 * If window is closed can only take segments at 1516 * window edge, and have to drop data and PUSH from 1517 * incoming segments. Continue processing, but 1518 * remember to ack. Otherwise, drop segment 1519 * and ack. 1520 */ 1521 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1522 tp->t_flags |= TF_ACKNOW; 1523 tcpstat.tcps_rcvwinprobe++; 1524 } else 1525 goto dropafterack; 1526 } else 1527 tcpstat.tcps_rcvbyteafterwin += todrop; 1528 m_adj(m, -todrop); 1529 tlen -= todrop; 1530 thflags &= ~(TH_PUSH|TH_FIN); 1531 } 1532 1533 /* 1534 * If last ACK falls within this segment's sequence numbers, 1535 * record its timestamp. 1536 * NOTE that the test is modified according to the latest 1537 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1538 */ 1539 if ((to.to_flags & TOF_TS) != 0 && 1540 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1541 tp->ts_recent_age = ticks; 1542 tp->ts_recent = to.to_tsval; 1543 } 1544 1545 /* 1546 * If a SYN is in the window, then this is an 1547 * error and we send an RST and drop the connection. 1548 */ 1549 if (thflags & TH_SYN) { 1550 tp = tcp_drop(tp, ECONNRESET); 1551 rstreason = BANDLIM_UNLIMITED; 1552 goto dropwithreset; 1553 } 1554 1555 /* 1556 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1557 * flag is on (half-synchronized state), then queue data for 1558 * later processing; else drop segment and return. 1559 */ 1560 if ((thflags & TH_ACK) == 0) { 1561 if (tp->t_state == TCPS_SYN_RECEIVED || 1562 (tp->t_flags & TF_NEEDSYN)) 1563 goto step6; 1564 else 1565 goto drop; 1566 } 1567 1568 /* 1569 * Ack processing. 1570 */ 1571 switch (tp->t_state) { 1572 1573 /* 1574 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1575 * ESTABLISHED state and continue processing. 1576 * The ACK was checked above. 1577 */ 1578 case TCPS_SYN_RECEIVED: 1579 1580 tcpstat.tcps_connects++; 1581 soisconnected(so); 1582 /* Do window scaling? */ 1583 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1584 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1585 tp->snd_scale = tp->requested_s_scale; 1586 tp->rcv_scale = tp->request_r_scale; 1587 } 1588 /* 1589 * Upon successful completion of 3-way handshake, 1590 * update cache.CC if it was undefined, pass any queued 1591 * data to the user, and advance state appropriately. 1592 */ 1593 if ((taop = tcp_gettaocache(&inp->inp_inc)) != NULL && 1594 taop->tao_cc == 0) 1595 taop->tao_cc = tp->cc_recv; 1596 1597 /* 1598 * Make transitions: 1599 * SYN-RECEIVED -> ESTABLISHED 1600 * SYN-RECEIVED* -> FIN-WAIT-1 1601 */ 1602 tp->t_starttime = ticks; 1603 if (tp->t_flags & TF_NEEDFIN) { 1604 tp->t_state = TCPS_FIN_WAIT_1; 1605 tp->t_flags &= ~TF_NEEDFIN; 1606 } else { 1607 tp->t_state = TCPS_ESTABLISHED; 1608 callout_reset(tp->tt_keep, tcp_keepidle, 1609 tcp_timer_keep, tp); 1610 } 1611 /* 1612 * If segment contains data or ACK, will call tcp_reass() 1613 * later; if not, do so now to pass queued data to user. 1614 */ 1615 if (tlen == 0 && (thflags & TH_FIN) == 0) 1616 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 1617 (struct mbuf *)0); 1618 tp->snd_wl1 = th->th_seq - 1; 1619 /* fall into ... */ 1620 1621 /* 1622 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1623 * ACKs. If the ack is in the range 1624 * tp->snd_una < th->th_ack <= tp->snd_max 1625 * then advance tp->snd_una to th->th_ack and drop 1626 * data from the retransmission queue. If this ACK reflects 1627 * more up to date window information we update our window information. 1628 */ 1629 case TCPS_ESTABLISHED: 1630 case TCPS_FIN_WAIT_1: 1631 case TCPS_FIN_WAIT_2: 1632 case TCPS_CLOSE_WAIT: 1633 case TCPS_CLOSING: 1634 case TCPS_LAST_ACK: 1635 case TCPS_TIME_WAIT: 1636 1637 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1638 if (tlen == 0 && tiwin == tp->snd_wnd) { 1639 tcpstat.tcps_rcvdupack++; 1640 /* 1641 * If we have outstanding data (other than 1642 * a window probe), this is a completely 1643 * duplicate ack (ie, window info didn't 1644 * change), the ack is the biggest we've 1645 * seen and we've seen exactly our rexmt 1646 * threshhold of them, assume a packet 1647 * has been dropped and retransmit it. 1648 * Kludge snd_nxt & the congestion 1649 * window so we send only this one 1650 * packet. 1651 * 1652 * We know we're losing at the current 1653 * window size so do congestion avoidance 1654 * (set ssthresh to half the current window 1655 * and pull our congestion window back to 1656 * the new ssthresh). 1657 * 1658 * Dup acks mean that packets have left the 1659 * network (they're now cached at the receiver) 1660 * so bump cwnd by the amount in the receiver 1661 * to keep a constant cwnd packets in the 1662 * network. 1663 */ 1664 if (!callout_active(tp->tt_rexmt) || 1665 th->th_ack != tp->snd_una) 1666 tp->t_dupacks = 0; 1667 else if (++tp->t_dupacks > tcprexmtthresh || 1668 (tcp_do_newreno && 1669 SEQ_LT(tp->snd_una, 1670 tp->snd_recover))) { 1671 tp->snd_cwnd += tp->t_maxseg; 1672 (void) tcp_output(tp); 1673 goto drop; 1674 } else if (tp->t_dupacks == tcprexmtthresh) { 1675 tcp_seq onxt = tp->snd_nxt; 1676 u_int win; 1677 if (tcp_do_newreno && 1678 SEQ_LEQ(th->th_ack, tp->snd_high)) { 1679 tp->t_dupacks = 0; 1680 break; 1681 } 1682 win = min(tp->snd_wnd, tp->snd_cwnd) / 1683 2 / tp->t_maxseg; 1684 if (win < 2) 1685 win = 2; 1686 tp->snd_ssthresh = win * tp->t_maxseg; 1687 tp->snd_recover = tp->snd_max; 1688 callout_stop(tp->tt_rexmt); 1689 tp->t_rtttime = 0; 1690 tp->snd_nxt = th->th_ack; 1691 tp->snd_cwnd = tp->t_maxseg; 1692 (void) tcp_output(tp); 1693 tp->snd_cwnd = tp->snd_ssthresh + 1694 tp->t_maxseg * tp->t_dupacks; 1695 if (SEQ_GT(onxt, tp->snd_nxt)) 1696 tp->snd_nxt = onxt; 1697 goto drop; 1698 } 1699 } else 1700 tp->t_dupacks = 0; 1701 break; 1702 } 1703 1704 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); 1705 1706 /* 1707 * If the congestion window was inflated to account 1708 * for the other side's cached packets, retract it. 1709 */ 1710 if (tcp_do_newreno) { 1711 if (SEQ_LT(tp->snd_una, tp->snd_recover)) { 1712 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 1713 tcp_newreno_partial_ack(tp, th); 1714 } else { 1715 /* 1716 * Window inflation should have left us 1717 * with approximately snd_ssthresh 1718 * outstanding data. 1719 * But in case we would be inclined to 1720 * send a burst, better to do it via 1721 * the slow start mechanism. 1722 */ 1723 if (SEQ_GT(th->th_ack + 1724 tp->snd_ssthresh, 1725 tp->snd_max)) 1726 tp->snd_cwnd = tp->snd_max - 1727 th->th_ack + 1728 tp->t_maxseg; 1729 else 1730 tp->snd_cwnd = tp->snd_ssthresh; 1731 } 1732 } 1733 } else { 1734 if (tp->t_dupacks >= tcprexmtthresh && 1735 tp->snd_cwnd > tp->snd_ssthresh) 1736 tp->snd_cwnd = tp->snd_ssthresh; 1737 } 1738 tp->t_dupacks = 0; 1739 if (SEQ_GT(th->th_ack, tp->snd_max)) { 1740 tcpstat.tcps_rcvacktoomuch++; 1741 goto dropafterack; 1742 } 1743 /* 1744 * If we reach this point, ACK is not a duplicate, 1745 * i.e., it ACKs something we sent. 1746 */ 1747 if (tp->t_flags & TF_NEEDSYN) { 1748 /* 1749 * T/TCP: Connection was half-synchronized, and our 1750 * SYN has been ACK'd (so connection is now fully 1751 * synchronized). Go to non-starred state, 1752 * increment snd_una for ACK of SYN, and check if 1753 * we can do window scaling. 1754 */ 1755 tp->t_flags &= ~TF_NEEDSYN; 1756 tp->snd_una++; 1757 /* Do window scaling? */ 1758 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1759 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1760 tp->snd_scale = tp->requested_s_scale; 1761 tp->rcv_scale = tp->request_r_scale; 1762 } 1763 } 1764 1765 process_ACK: 1766 acked = th->th_ack - tp->snd_una; 1767 tcpstat.tcps_rcvackpack++; 1768 tcpstat.tcps_rcvackbyte += acked; 1769 1770 /* 1771 * If we just performed our first retransmit, and the ACK 1772 * arrives within our recovery window, then it was a mistake 1773 * to do the retransmit in the first place. Recover our 1774 * original cwnd and ssthresh, and proceed to transmit where 1775 * we left off. 1776 */ 1777 if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 1778 tp->snd_cwnd = tp->snd_cwnd_prev; 1779 tp->snd_ssthresh = tp->snd_ssthresh_prev; 1780 tp->snd_high = tp->snd_high_prev; 1781 tp->snd_nxt = tp->snd_max; 1782 tp->t_badrxtwin = 0; /* XXX probably not required */ 1783 } 1784 1785 /* 1786 * If we have a timestamp reply, update smoothed 1787 * round trip time. If no timestamp is present but 1788 * transmit timer is running and timed sequence 1789 * number was acked, update smoothed round trip time. 1790 * Since we now have an rtt measurement, cancel the 1791 * timer backoff (cf., Phil Karn's retransmit alg.). 1792 * Recompute the initial retransmit timer. 1793 * 1794 * Some machines (certain windows boxes) send broken 1795 * timestamp replies during the SYN+ACK phase, ignore 1796 * timestamps of 0. 1797 */ 1798 if ((to.to_flags & TOF_TS) != 0 && 1799 to.to_tsecr) { 1800 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 1801 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 1802 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 1803 } 1804 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1805 1806 /* 1807 * If all outstanding data is acked, stop retransmit 1808 * timer and remember to restart (more output or persist). 1809 * If there is more data to be acked, restart retransmit 1810 * timer, using current (possibly backed-off) value. 1811 */ 1812 if (th->th_ack == tp->snd_max) { 1813 callout_stop(tp->tt_rexmt); 1814 needoutput = 1; 1815 } else if (!callout_active(tp->tt_persist)) 1816 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 1817 tcp_timer_rexmt, tp); 1818 1819 /* 1820 * If no data (only SYN) was ACK'd, 1821 * skip rest of ACK processing. 1822 */ 1823 if (acked == 0) 1824 goto step6; 1825 1826 /* 1827 * When new data is acked, open the congestion window. 1828 * If the window gives us less than ssthresh packets 1829 * in flight, open exponentially (maxseg per packet). 1830 * Otherwise open linearly: maxseg per window 1831 * (maxseg^2 / cwnd per packet). 1832 */ 1833 if (!tcp_do_newreno || SEQ_GEQ(tp->snd_una, tp->snd_recover)) { 1834 register u_int cw = tp->snd_cwnd; 1835 register u_int incr = tp->t_maxseg; 1836 if (cw > tp->snd_ssthresh) 1837 incr = incr * incr / cw; 1838 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale); 1839 } 1840 if (acked > so->so_snd.sb_cc) { 1841 tp->snd_wnd -= so->so_snd.sb_cc; 1842 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); 1843 ourfinisacked = 1; 1844 } else { 1845 sbdrop(&so->so_snd, acked); 1846 tp->snd_wnd -= acked; 1847 ourfinisacked = 0; 1848 } 1849 sowwakeup(so); 1850 /* detect una wraparound */ 1851 if (SEQ_GEQ(tp->snd_una, tp->snd_recover) && 1852 SEQ_LT(th->th_ack, tp->snd_recover)) 1853 tp->snd_recover = th->th_ack; 1854 if (SEQ_GT(tp->snd_una, tp->snd_high) && 1855 SEQ_LEQ(th->th_ack, tp->snd_high)) 1856 tp->snd_high = th->th_ack - 1; 1857 tp->snd_una = th->th_ack; 1858 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 1859 tp->snd_nxt = tp->snd_una; 1860 1861 switch (tp->t_state) { 1862 1863 /* 1864 * In FIN_WAIT_1 STATE in addition to the processing 1865 * for the ESTABLISHED state if our FIN is now acknowledged 1866 * then enter FIN_WAIT_2. 1867 */ 1868 case TCPS_FIN_WAIT_1: 1869 if (ourfinisacked) { 1870 /* 1871 * If we can't receive any more 1872 * data, then closing user can proceed. 1873 * Starting the timer is contrary to the 1874 * specification, but if we don't get a FIN 1875 * we'll hang forever. 1876 */ 1877 if (so->so_state & SS_CANTRCVMORE) { 1878 soisdisconnected(so); 1879 callout_reset(tp->tt_2msl, tcp_maxidle, 1880 tcp_timer_2msl, tp); 1881 } 1882 tp->t_state = TCPS_FIN_WAIT_2; 1883 } 1884 break; 1885 1886 /* 1887 * In CLOSING STATE in addition to the processing for 1888 * the ESTABLISHED state if the ACK acknowledges our FIN 1889 * then enter the TIME-WAIT state, otherwise ignore 1890 * the segment. 1891 */ 1892 case TCPS_CLOSING: 1893 if (ourfinisacked) { 1894 tp->t_state = TCPS_TIME_WAIT; 1895 tcp_canceltimers(tp); 1896 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 1897 if (tp->cc_recv != 0 && 1898 (ticks - tp->t_starttime) < tcp_msl) 1899 callout_reset(tp->tt_2msl, 1900 tp->t_rxtcur * 1901 TCPTV_TWTRUNC, 1902 tcp_timer_2msl, tp); 1903 else 1904 callout_reset(tp->tt_2msl, 2 * tcp_msl, 1905 tcp_timer_2msl, tp); 1906 soisdisconnected(so); 1907 } 1908 break; 1909 1910 /* 1911 * In LAST_ACK, we may still be waiting for data to drain 1912 * and/or to be acked, as well as for the ack of our FIN. 1913 * If our FIN is now acknowledged, delete the TCB, 1914 * enter the closed state and return. 1915 */ 1916 case TCPS_LAST_ACK: 1917 if (ourfinisacked) { 1918 tp = tcp_close(tp); 1919 goto drop; 1920 } 1921 break; 1922 1923 /* 1924 * In TIME_WAIT state the only thing that should arrive 1925 * is a retransmission of the remote FIN. Acknowledge 1926 * it and restart the finack timer. 1927 */ 1928 case TCPS_TIME_WAIT: 1929 callout_reset(tp->tt_2msl, 2 * tcp_msl, 1930 tcp_timer_2msl, tp); 1931 goto dropafterack; 1932 } 1933 } 1934 1935 step6: 1936 /* 1937 * Update window information. 1938 * Don't look at window if no ACK: TAC's send garbage on first SYN. 1939 */ 1940 if ((thflags & TH_ACK) && 1941 (SEQ_LT(tp->snd_wl1, th->th_seq) || 1942 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 1943 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 1944 /* keep track of pure window updates */ 1945 if (tlen == 0 && 1946 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 1947 tcpstat.tcps_rcvwinupd++; 1948 tp->snd_wnd = tiwin; 1949 tp->snd_wl1 = th->th_seq; 1950 tp->snd_wl2 = th->th_ack; 1951 if (tp->snd_wnd > tp->max_sndwnd) 1952 tp->max_sndwnd = tp->snd_wnd; 1953 needoutput = 1; 1954 } 1955 1956 /* 1957 * Process segments with URG. 1958 */ 1959 if ((thflags & TH_URG) && th->th_urp && 1960 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1961 /* 1962 * This is a kludge, but if we receive and accept 1963 * random urgent pointers, we'll crash in 1964 * soreceive. It's hard to imagine someone 1965 * actually wanting to send this much urgent data. 1966 */ 1967 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 1968 th->th_urp = 0; /* XXX */ 1969 thflags &= ~TH_URG; /* XXX */ 1970 goto dodata; /* XXX */ 1971 } 1972 /* 1973 * If this segment advances the known urgent pointer, 1974 * then mark the data stream. This should not happen 1975 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 1976 * a FIN has been received from the remote side. 1977 * In these states we ignore the URG. 1978 * 1979 * According to RFC961 (Assigned Protocols), 1980 * the urgent pointer points to the last octet 1981 * of urgent data. We continue, however, 1982 * to consider it to indicate the first octet 1983 * of data past the urgent section as the original 1984 * spec states (in one of two places). 1985 */ 1986 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 1987 tp->rcv_up = th->th_seq + th->th_urp; 1988 so->so_oobmark = so->so_rcv.sb_cc + 1989 (tp->rcv_up - tp->rcv_nxt) - 1; 1990 if (so->so_oobmark == 0) 1991 so->so_state |= SS_RCVATMARK; 1992 sohasoutofband(so); 1993 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 1994 } 1995 /* 1996 * Remove out of band data so doesn't get presented to user. 1997 * This can happen independent of advancing the URG pointer, 1998 * but if two URG's are pending at once, some out-of-band 1999 * data may creep in... ick. 2000 */ 2001 if (th->th_urp <= (u_long)tlen 2002 #ifdef SO_OOBINLINE 2003 && (so->so_options & SO_OOBINLINE) == 0 2004 #endif 2005 ) 2006 tcp_pulloutofband(so, th, m, 2007 drop_hdrlen); /* hdr drop is delayed */ 2008 } else { 2009 /* 2010 * If no out of band data is expected, 2011 * pull receive urgent pointer along 2012 * with the receive window. 2013 */ 2014 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2015 tp->rcv_up = tp->rcv_nxt; 2016 } 2017 dodata: /* XXX */ 2018 2019 /* 2020 * Process the segment text, merging it into the TCP sequencing queue, 2021 * and arranging for acknowledgment of receipt if necessary. 2022 * This process logically involves adjusting tp->rcv_wnd as data 2023 * is presented to the user (this happens in tcp_usrreq.c, 2024 * case PRU_RCVD). If a FIN has already been received on this 2025 * connection then we just ignore the text. 2026 */ 2027 if ((tlen || (thflags & TH_FIN)) && 2028 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2029 m_adj(m, drop_hdrlen); /* delayed header drop */ 2030 /* 2031 * Insert segment which includes th into TCP reassembly queue 2032 * with control block tp. Set thflags to whether reassembly now 2033 * includes a segment with FIN. This handles the common case 2034 * inline (segment is the next to be received on an established 2035 * connection, and the queue is empty), avoiding linkage into 2036 * and removal from the queue and repetition of various 2037 * conversions. 2038 * Set DELACK for segments received in order, but ack 2039 * immediately when segments are out of order (so 2040 * fast retransmit can work). 2041 */ 2042 if (th->th_seq == tp->rcv_nxt && 2043 LIST_EMPTY(&tp->t_segq) && 2044 TCPS_HAVEESTABLISHED(tp->t_state)) { 2045 if (DELAY_ACK(tp)) 2046 callout_reset(tp->tt_delack, tcp_delacktime, 2047 tcp_timer_delack, tp); 2048 else 2049 tp->t_flags |= TF_ACKNOW; 2050 tp->rcv_nxt += tlen; 2051 thflags = th->th_flags & TH_FIN; 2052 tcpstat.tcps_rcvpack++; 2053 tcpstat.tcps_rcvbyte += tlen; 2054 ND6_HINT(tp); 2055 if (so->so_state & SS_CANTRCVMORE) 2056 m_freem(m); 2057 else 2058 sbappend(&so->so_rcv, m); 2059 sorwakeup(so); 2060 } else { 2061 thflags = tcp_reass(tp, th, &tlen, m); 2062 tp->t_flags |= TF_ACKNOW; 2063 } 2064 2065 /* 2066 * Note the amount of data that peer has sent into 2067 * our window, in order to estimate the sender's 2068 * buffer size. 2069 */ 2070 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2071 } else { 2072 m_freem(m); 2073 thflags &= ~TH_FIN; 2074 } 2075 2076 /* 2077 * If FIN is received ACK the FIN and let the user know 2078 * that the connection is closing. 2079 */ 2080 if (thflags & TH_FIN) { 2081 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2082 socantrcvmore(so); 2083 /* 2084 * If connection is half-synchronized 2085 * (ie NEEDSYN flag on) then delay ACK, 2086 * so it may be piggybacked when SYN is sent. 2087 * Otherwise, since we received a FIN then no 2088 * more input can be expected, send ACK now. 2089 */ 2090 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) 2091 callout_reset(tp->tt_delack, tcp_delacktime, 2092 tcp_timer_delack, tp); 2093 else 2094 tp->t_flags |= TF_ACKNOW; 2095 tp->rcv_nxt++; 2096 } 2097 switch (tp->t_state) { 2098 2099 /* 2100 * In SYN_RECEIVED and ESTABLISHED STATES 2101 * enter the CLOSE_WAIT state. 2102 */ 2103 case TCPS_SYN_RECEIVED: 2104 tp->t_starttime = ticks; 2105 /*FALLTHROUGH*/ 2106 case TCPS_ESTABLISHED: 2107 tp->t_state = TCPS_CLOSE_WAIT; 2108 break; 2109 2110 /* 2111 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2112 * enter the CLOSING state. 2113 */ 2114 case TCPS_FIN_WAIT_1: 2115 tp->t_state = TCPS_CLOSING; 2116 break; 2117 2118 /* 2119 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2120 * starting the time-wait timer, turning off the other 2121 * standard timers. 2122 */ 2123 case TCPS_FIN_WAIT_2: 2124 tp->t_state = TCPS_TIME_WAIT; 2125 tcp_canceltimers(tp); 2126 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 2127 if (tp->cc_recv != 0 && 2128 (ticks - tp->t_starttime) < tcp_msl) { 2129 callout_reset(tp->tt_2msl, 2130 tp->t_rxtcur * TCPTV_TWTRUNC, 2131 tcp_timer_2msl, tp); 2132 /* For transaction client, force ACK now. */ 2133 tp->t_flags |= TF_ACKNOW; 2134 } 2135 else 2136 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2137 tcp_timer_2msl, tp); 2138 soisdisconnected(so); 2139 break; 2140 2141 /* 2142 * In TIME_WAIT state restart the 2 MSL time_wait timer. 2143 */ 2144 case TCPS_TIME_WAIT: 2145 callout_reset(tp->tt_2msl, 2 * tcp_msl, 2146 tcp_timer_2msl, tp); 2147 break; 2148 } 2149 } 2150 #ifdef TCPDEBUG 2151 if (so->so_options & SO_DEBUG) 2152 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2153 &tcp_savetcp, 0); 2154 #endif 2155 2156 /* 2157 * Return any desired output. 2158 */ 2159 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2160 (void) tcp_output(tp); 2161 return; 2162 2163 dropafterack: 2164 /* 2165 * Generate an ACK dropping incoming segment if it occupies 2166 * sequence space, where the ACK reflects our state. 2167 * 2168 * We can now skip the test for the RST flag since all 2169 * paths to this code happen after packets containing 2170 * RST have been dropped. 2171 * 2172 * In the SYN-RECEIVED state, don't send an ACK unless the 2173 * segment we received passes the SYN-RECEIVED ACK test. 2174 * If it fails send a RST. This breaks the loop in the 2175 * "LAND" DoS attack, and also prevents an ACK storm 2176 * between two listening ports that have been sent forged 2177 * SYN segments, each with the source address of the other. 2178 */ 2179 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2180 (SEQ_GT(tp->snd_una, th->th_ack) || 2181 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2182 rstreason = BANDLIM_RST_OPENPORT; 2183 goto dropwithreset; 2184 } 2185 #ifdef TCPDEBUG 2186 if (so->so_options & SO_DEBUG) 2187 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2188 &tcp_savetcp, 0); 2189 #endif 2190 m_freem(m); 2191 tp->t_flags |= TF_ACKNOW; 2192 (void) tcp_output(tp); 2193 return; 2194 2195 dropwithreset: 2196 /* 2197 * Generate a RST, dropping incoming segment. 2198 * Make ACK acceptable to originator of segment. 2199 * Don't bother to respond if destination was broadcast/multicast. 2200 */ 2201 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 2202 goto drop; 2203 if (isipv6) { 2204 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2205 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2206 goto drop; 2207 } else { 2208 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2209 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2210 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2211 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2212 goto drop; 2213 } 2214 /* IPv6 anycast check is done at tcp6_input() */ 2215 2216 /* 2217 * Perform bandwidth limiting. 2218 */ 2219 #ifdef ICMP_BANDLIM 2220 if (badport_bandlim(rstreason) < 0) 2221 goto drop; 2222 #endif 2223 2224 #ifdef TCPDEBUG 2225 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2226 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2227 &tcp_savetcp, 0); 2228 #endif 2229 if (thflags & TH_ACK) 2230 /* mtod() below is safe as long as hdr dropping is delayed */ 2231 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, 2232 TH_RST); 2233 else { 2234 if (thflags & TH_SYN) 2235 tlen++; 2236 /* mtod() below is safe as long as hdr dropping is delayed */ 2237 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 2238 (tcp_seq)0, TH_RST|TH_ACK); 2239 } 2240 return; 2241 2242 drop: 2243 /* 2244 * Drop space held by incoming segment and return. 2245 */ 2246 #ifdef TCPDEBUG 2247 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2248 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2249 &tcp_savetcp, 0); 2250 #endif 2251 m_freem(m); 2252 return; 2253 } 2254 2255 /* 2256 * Parse TCP options and place in tcpopt. 2257 */ 2258 static void 2259 tcp_dooptions(to, cp, cnt, is_syn) 2260 struct tcpopt *to; 2261 u_char *cp; 2262 int cnt; 2263 { 2264 int opt, optlen; 2265 2266 to->to_flags = 0; 2267 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2268 opt = cp[0]; 2269 if (opt == TCPOPT_EOL) 2270 break; 2271 if (opt == TCPOPT_NOP) 2272 optlen = 1; 2273 else { 2274 if (cnt < 2) 2275 break; 2276 optlen = cp[1]; 2277 if (optlen < 2 || optlen > cnt) 2278 break; 2279 } 2280 switch (opt) { 2281 case TCPOPT_MAXSEG: 2282 if (optlen != TCPOLEN_MAXSEG) 2283 continue; 2284 if (!is_syn) 2285 continue; 2286 to->to_flags |= TOF_MSS; 2287 bcopy((char *)cp + 2, 2288 (char *)&to->to_mss, sizeof(to->to_mss)); 2289 to->to_mss = ntohs(to->to_mss); 2290 break; 2291 case TCPOPT_WINDOW: 2292 if (optlen != TCPOLEN_WINDOW) 2293 continue; 2294 if (! is_syn) 2295 continue; 2296 to->to_flags |= TOF_SCALE; 2297 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 2298 break; 2299 case TCPOPT_TIMESTAMP: 2300 if (optlen != TCPOLEN_TIMESTAMP) 2301 continue; 2302 to->to_flags |= TOF_TS; 2303 bcopy((char *)cp + 2, 2304 (char *)&to->to_tsval, sizeof(to->to_tsval)); 2305 to->to_tsval = ntohl(to->to_tsval); 2306 bcopy((char *)cp + 6, 2307 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 2308 to->to_tsecr = ntohl(to->to_tsecr); 2309 break; 2310 case TCPOPT_CC: 2311 if (optlen != TCPOLEN_CC) 2312 continue; 2313 to->to_flags |= TOF_CC; 2314 bcopy((char *)cp + 2, 2315 (char *)&to->to_cc, sizeof(to->to_cc)); 2316 to->to_cc = ntohl(to->to_cc); 2317 break; 2318 case TCPOPT_CCNEW: 2319 if (optlen != TCPOLEN_CC) 2320 continue; 2321 if (!is_syn) 2322 continue; 2323 to->to_flags |= TOF_CCNEW; 2324 bcopy((char *)cp + 2, 2325 (char *)&to->to_cc, sizeof(to->to_cc)); 2326 to->to_cc = ntohl(to->to_cc); 2327 break; 2328 case TCPOPT_CCECHO: 2329 if (optlen != TCPOLEN_CC) 2330 continue; 2331 if (!is_syn) 2332 continue; 2333 to->to_flags |= TOF_CCECHO; 2334 bcopy((char *)cp + 2, 2335 (char *)&to->to_ccecho, sizeof(to->to_ccecho)); 2336 to->to_ccecho = ntohl(to->to_ccecho); 2337 break; 2338 default: 2339 continue; 2340 } 2341 } 2342 } 2343 2344 /* 2345 * Pull out of band byte out of a segment so 2346 * it doesn't appear in the user's data queue. 2347 * It is still reflected in the segment length for 2348 * sequencing purposes. 2349 */ 2350 static void 2351 tcp_pulloutofband(so, th, m, off) 2352 struct socket *so; 2353 struct tcphdr *th; 2354 register struct mbuf *m; 2355 int off; /* delayed to be droped hdrlen */ 2356 { 2357 int cnt = off + th->th_urp - 1; 2358 2359 while (cnt >= 0) { 2360 if (m->m_len > cnt) { 2361 char *cp = mtod(m, caddr_t) + cnt; 2362 struct tcpcb *tp = sototcpcb(so); 2363 2364 tp->t_iobc = *cp; 2365 tp->t_oobflags |= TCPOOB_HAVEDATA; 2366 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 2367 m->m_len--; 2368 if (m->m_flags & M_PKTHDR) 2369 m->m_pkthdr.len--; 2370 return; 2371 } 2372 cnt -= m->m_len; 2373 m = m->m_next; 2374 if (m == 0) 2375 break; 2376 } 2377 panic("tcp_pulloutofband"); 2378 } 2379 2380 /* 2381 * Collect new round-trip time estimate 2382 * and update averages and current timeout. 2383 */ 2384 static void 2385 tcp_xmit_timer(tp, rtt) 2386 register struct tcpcb *tp; 2387 int rtt; 2388 { 2389 register int delta; 2390 2391 tcpstat.tcps_rttupdated++; 2392 tp->t_rttupdated++; 2393 if (tp->t_srtt != 0) { 2394 /* 2395 * srtt is stored as fixed point with 5 bits after the 2396 * binary point (i.e., scaled by 8). The following magic 2397 * is equivalent to the smoothing algorithm in rfc793 with 2398 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2399 * point). Adjust rtt to origin 0. 2400 */ 2401 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2402 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2403 2404 if ((tp->t_srtt += delta) <= 0) 2405 tp->t_srtt = 1; 2406 2407 /* 2408 * We accumulate a smoothed rtt variance (actually, a 2409 * smoothed mean difference), then set the retransmit 2410 * timer to smoothed rtt + 4 times the smoothed variance. 2411 * rttvar is stored as fixed point with 4 bits after the 2412 * binary point (scaled by 16). The following is 2413 * equivalent to rfc793 smoothing with an alpha of .75 2414 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2415 * rfc793's wired-in beta. 2416 */ 2417 if (delta < 0) 2418 delta = -delta; 2419 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2420 if ((tp->t_rttvar += delta) <= 0) 2421 tp->t_rttvar = 1; 2422 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2423 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2424 } else { 2425 /* 2426 * No rtt measurement yet - use the unsmoothed rtt. 2427 * Set the variance to half the rtt (so our first 2428 * retransmit happens at 3*rtt). 2429 */ 2430 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2431 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2432 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2433 } 2434 tp->t_rtttime = 0; 2435 tp->t_rxtshift = 0; 2436 2437 /* 2438 * the retransmit should happen at rtt + 4 * rttvar. 2439 * Because of the way we do the smoothing, srtt and rttvar 2440 * will each average +1/2 tick of bias. When we compute 2441 * the retransmit timer, we want 1/2 tick of rounding and 2442 * 1 extra tick because of +-1/2 tick uncertainty in the 2443 * firing of the timer. The bias will give us exactly the 2444 * 1.5 tick we need. But, because the bias is 2445 * statistical, we have to test that we don't drop below 2446 * the minimum feasible timer (which is 2 ticks). 2447 */ 2448 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2449 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2450 2451 /* 2452 * We received an ack for a packet that wasn't retransmitted; 2453 * it is probably safe to discard any error indications we've 2454 * received recently. This isn't quite right, but close enough 2455 * for now (a route might have failed after we sent a segment, 2456 * and the return path might not be symmetrical). 2457 */ 2458 tp->t_softerror = 0; 2459 } 2460 2461 /* 2462 * Determine a reasonable value for maxseg size. 2463 * If the route is known, check route for mtu. 2464 * If none, use an mss that can be handled on the outgoing 2465 * interface without forcing IP to fragment; if bigger than 2466 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2467 * to utilize large mbufs. If no route is found, route has no mtu, 2468 * or the destination isn't local, use a default, hopefully conservative 2469 * size (usually 512 or the default IP max size, but no more than the mtu 2470 * of the interface), as we can't discover anything about intervening 2471 * gateways or networks. We also initialize the congestion/slow start 2472 * window to be a single segment if the destination isn't local. 2473 * While looking at the routing entry, we also initialize other path-dependent 2474 * parameters from pre-set or cached values in the routing entry. 2475 * 2476 * Also take into account the space needed for options that we 2477 * send regularly. Make maxseg shorter by that amount to assure 2478 * that we can send maxseg amount of data even when the options 2479 * are present. Store the upper limit of the length of options plus 2480 * data in maxopd. 2481 * 2482 * NOTE that this routine is only called when we process an incoming 2483 * segment, for outgoing segments only tcp_mssopt is called. 2484 * 2485 * In case of T/TCP, we call this routine during implicit connection 2486 * setup as well (offer = -1), to initialize maxseg from the cached 2487 * MSS of our peer. 2488 */ 2489 void 2490 tcp_mss(tp, offer) 2491 struct tcpcb *tp; 2492 int offer; 2493 { 2494 register struct rtentry *rt; 2495 struct ifnet *ifp; 2496 register int rtt, mss; 2497 u_long bufsize; 2498 struct inpcb *inp = tp->t_inpcb; 2499 struct socket *so; 2500 struct rmxp_tao *taop; 2501 int origoffer = offer; 2502 #ifdef INET6 2503 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2504 size_t min_protoh = isipv6 ? 2505 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2506 sizeof(struct tcpiphdr); 2507 #else 2508 const int isipv6 = 0; 2509 const size_t min_protoh = sizeof(struct tcpiphdr); 2510 #endif 2511 2512 if (isipv6) 2513 rt = tcp_rtlookup6(&inp->inp_inc); 2514 else 2515 rt = tcp_rtlookup(&inp->inp_inc); 2516 if (rt == NULL) { 2517 tp->t_maxopd = tp->t_maxseg = 2518 isipv6 ? tcp_v6mssdflt : tcp_mssdflt; 2519 return; 2520 } 2521 ifp = rt->rt_ifp; 2522 so = inp->inp_socket; 2523 2524 taop = rmx_taop(rt->rt_rmx); 2525 /* 2526 * Offer == -1 means that we didn't receive SYN yet, 2527 * use cached value in that case; 2528 */ 2529 if (offer == -1) 2530 offer = taop->tao_mssopt; 2531 /* 2532 * Offer == 0 means that there was no MSS on the SYN segment, 2533 * in this case we use tcp_mssdflt. 2534 */ 2535 if (offer == 0) 2536 offer = isipv6 ? tcp_v6mssdflt : tcp_mssdflt; 2537 else 2538 /* 2539 * Sanity check: make sure that maxopd will be large 2540 * enough to allow some data on segments even is the 2541 * all the option space is used (40bytes). Otherwise 2542 * funny things may happen in tcp_output. 2543 */ 2544 offer = max(offer, 64); 2545 taop->tao_mssopt = offer; 2546 2547 /* 2548 * While we're here, check if there's an initial rtt 2549 * or rttvar. Convert from the route-table units 2550 * to scaled multiples of the slow timeout timer. 2551 */ 2552 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 2553 /* 2554 * XXX the lock bit for RTT indicates that the value 2555 * is also a minimum value; this is subject to time. 2556 */ 2557 if (rt->rt_rmx.rmx_locks & RTV_RTT) 2558 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); 2559 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); 2560 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 2561 tcpstat.tcps_usedrtt++; 2562 if (rt->rt_rmx.rmx_rttvar) { 2563 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 2564 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); 2565 tcpstat.tcps_usedrttvar++; 2566 } else { 2567 /* default variation is +- 1 rtt */ 2568 tp->t_rttvar = 2569 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 2570 } 2571 TCPT_RANGESET(tp->t_rxtcur, 2572 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 2573 tp->t_rttmin, TCPTV_REXMTMAX); 2574 } 2575 /* 2576 * if there's an mtu associated with the route, use it 2577 * else, use the link mtu. 2578 */ 2579 if (rt->rt_rmx.rmx_mtu) 2580 mss = rt->rt_rmx.rmx_mtu - min_protoh; 2581 else { 2582 if (isipv6) { 2583 mss = nd_ifinfo[rt->rt_ifp->if_index].linkmtu - 2584 min_protoh; 2585 if (!in6_localaddr(&inp->in6p_faddr)) 2586 mss = min(mss, tcp_v6mssdflt); 2587 } else { 2588 mss = ifp->if_mtu - min_protoh; 2589 if (!in_localaddr(inp->inp_faddr)) 2590 mss = min(mss, tcp_mssdflt); 2591 } 2592 } 2593 mss = min(mss, offer); 2594 /* 2595 * maxopd stores the maximum length of data AND options 2596 * in a segment; maxseg is the amount of data in a normal 2597 * segment. We need to store this value (maxopd) apart 2598 * from maxseg, because now every segment carries options 2599 * and thus we normally have somewhat less data in segments. 2600 */ 2601 tp->t_maxopd = mss; 2602 2603 /* 2604 * In case of T/TCP, origoffer==-1 indicates, that no segments 2605 * were received yet. In this case we just guess, otherwise 2606 * we do the same as before T/TCP. 2607 */ 2608 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 2609 (origoffer == -1 || 2610 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2611 mss -= TCPOLEN_TSTAMP_APPA; 2612 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 2613 (origoffer == -1 || 2614 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)) 2615 mss -= TCPOLEN_CC_APPA; 2616 2617 #if (MCLBYTES & (MCLBYTES - 1)) == 0 2618 if (mss > MCLBYTES) 2619 mss &= ~(MCLBYTES-1); 2620 #else 2621 if (mss > MCLBYTES) 2622 mss = mss / MCLBYTES * MCLBYTES; 2623 #endif 2624 /* 2625 * If there's a pipesize, change the socket buffer 2626 * to that size. Make the socket buffers an integral 2627 * number of mss units; if the mss is larger than 2628 * the socket buffer, decrease the mss. 2629 */ 2630 #ifdef RTV_SPIPE 2631 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 2632 #endif 2633 bufsize = so->so_snd.sb_hiwat; 2634 if (bufsize < mss) 2635 mss = bufsize; 2636 else { 2637 bufsize = roundup(bufsize, mss); 2638 if (bufsize > sb_max) 2639 bufsize = sb_max; 2640 if (bufsize > so->so_snd.sb_hiwat) 2641 (void)sbreserve(&so->so_snd, bufsize, so, NULL); 2642 } 2643 tp->t_maxseg = mss; 2644 2645 #ifdef RTV_RPIPE 2646 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 2647 #endif 2648 bufsize = so->so_rcv.sb_hiwat; 2649 if (bufsize > mss) { 2650 bufsize = roundup(bufsize, mss); 2651 if (bufsize > sb_max) 2652 bufsize = sb_max; 2653 if (bufsize > so->so_rcv.sb_hiwat) 2654 (void)sbreserve(&so->so_rcv, bufsize, so, NULL); 2655 } 2656 2657 /* 2658 * Set the slow-start flight size depending on whether this 2659 * is a local network or not. 2660 */ 2661 if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 2662 (!isipv6 && in_localaddr(inp->inp_faddr))) 2663 tp->snd_cwnd = mss * ss_fltsz_local; 2664 else 2665 tp->snd_cwnd = mss * ss_fltsz; 2666 2667 if (rt->rt_rmx.rmx_ssthresh) { 2668 /* 2669 * There's some sort of gateway or interface 2670 * buffer limit on the path. Use this to set 2671 * the slow start threshhold, but set the 2672 * threshold to no less than 2*mss. 2673 */ 2674 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 2675 tcpstat.tcps_usedssthresh++; 2676 } 2677 } 2678 2679 /* 2680 * Determine the MSS option to send on an outgoing SYN. 2681 */ 2682 int 2683 tcp_mssopt(tp) 2684 struct tcpcb *tp; 2685 { 2686 struct rtentry *rt; 2687 #ifdef INET6 2688 int isipv6 = ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2689 int min_protoh = isipv6 ? 2690 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : 2691 sizeof(struct tcpiphdr); 2692 #else 2693 const int isipv6 = 0; 2694 const size_t min_protoh = sizeof(struct tcpiphdr); 2695 #endif 2696 2697 if (isipv6) 2698 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc); 2699 else 2700 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc); 2701 if (rt == NULL) 2702 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); 2703 2704 return (rt->rt_ifp->if_mtu - min_protoh); 2705 } 2706 2707 2708 /* 2709 * When a partial ack arrives, force the retransmission of the 2710 * next unacknowledged segment. Do not clear tp->t_dupacks. 2711 * By setting snd_nxt to ti_ack, this forces retransmission timer to 2712 * be started again. 2713 */ 2714 static void 2715 tcp_newreno_partial_ack(tp, th) 2716 struct tcpcb *tp; 2717 struct tcphdr *th; 2718 { 2719 tcp_seq onxt = tp->snd_nxt; 2720 u_long ocwnd = tp->snd_cwnd; 2721 2722 callout_stop(tp->tt_rexmt); 2723 tp->t_rtttime = 0; 2724 tp->snd_nxt = th->th_ack; 2725 /* 2726 * Set snd_cwnd to one segment beyond acknowledged offset 2727 * (tp->snd_una has not yet been updated when this function is called.) 2728 */ 2729 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); 2730 tp->t_flags |= TF_ACKNOW; 2731 (void) tcp_output(tp); 2732 tp->snd_cwnd = ocwnd; 2733 if (SEQ_GT(onxt, tp->snd_nxt)) 2734 tp->snd_nxt = onxt; 2735 /* 2736 * Partial window deflation. Relies on fact that tp->snd_una 2737 * not updated yet. 2738 */ 2739 tp->snd_cwnd -= (th->th_ack - tp->snd_una - tp->t_maxseg); 2740 } 2741